Mechanical counting fuze

ABSTRACT

1. A fuze comprising A BODY WITH AN UPPER AND A LOWER END HAVING A MAIN AXIAL BORE THERETHROUGH, SAID BODY LOWER END HAVING AN AXIAL BORE SMALLER THAN SAID MAIN BORE AND HAVING RADIAL GROOVE MEANS IN THE WALL DEFINING SAID SMALLER BORE, A HOLLOW OUTER PLUNGER MEMBER SLIDABLY MOUNTED IN SAID MAIN BORE, AN INNER PLUNGER MEMBER MOVABLY MOUNTED IN SAID OUTER PLUNGER MEMBER AND COAXIAL THERETHROUGH, A FIRING PIN RELEASABLY SECURED TO THE LOWER END OF SAID INNER PLUNGER MEMBER, CAM MEANS FIXED ON THE END OF SAID OUTER PLUNGER MEMBER, CAM FOLLOWER MEANS CARRIED BY SAID INNER PLUNGER MEMBER SO CONSTRUCTED AND ARRANGED THAT UPON RELATIVE DOWNWARDLY DIRECTED AXIAL MOVEMENT OF SAID OUTER PLUNGER MEMBER WITH RESPECT TO SAID BODY THE CAM MEANS WILL ACT ON SAID FOLLOWER MEANS TO IMPART A LIMITED ROTATIONAL MOVEMENT TO SAID INNER PLUNGER MEMBER, MEANS PREVENTING ROTATIONAL MOVEMENT OF THE OUTER PLUNGER MEMBER WITH RESPECT TO SAID BODY, A RESILIENT MEANS OPERATIVE BETWEEN SAID FIRING PIN AND SAID INNER PLUNGER MEMBER, SAID RESILIENT MEANS ARRANGED TO OPPOSE RELATIVE DOWNWARDLY DIRECTED AXIAL MOVEMENT OF SAID INNER PLUNGER MEMBER WITH RESPECT TO SAID BODY, TAB MEANS RADIALLY FIXED ON SAID FIRING PIN AND SO ARRANGED AND CONSTRUCTED AS TO ALIGN WITH SAID GROOVE MEANS WHEN SAID INNER PLUNGER MEMBER IS ROTATIONALLY ADVANCED WITH RESPECT TO SAID OUTER PLUNGER MEMBER BY A PREDETERMINED NUMBER OF AXIAL RECIPROCATIONS OF SAID OUTER PLUNGER MEMBER WHEREBY SAID FIRING PIN IS FREED TO MOVE DOWNWARDLY UNDER THE FORCE OF SAID RESILIENT MEANS.

United States Patent [72] Inventors Richard G. Thresher 651 Jennifer Lane, Aberdeen, Md. 21001; John P. Kosar, Apt. E6, Valley Stream Gardens, Denville, NJ. 07834; James F. Harper, 400 Strafford Ave., Wayne, Pa.

19087 Appl. No. 444,520 Filed Mar. 30, 1965 Patented Oct. 19, 1971 MECHANICAL COUNTING FUZE Primary ExaminerBenjamin A. Borchelt Assistant Examiner-Thomas H. Webb Attorneys-Harry M. Saragovitz, Edward J. Kelly, Herbert Berl and S. Dubrofi CLAIM: A fuze comprising a body with an upper and a lower end having a main axial bore therethrough, said body lower end having an axial bore smaller than said main bore and having radial groove means in the wall defining said smaller bore, a hollow outer plunger member slidably mounted in said main bore, an inner plunger member movably mounted in said outer plunger member and coaxial therethrough, a firing pin releasably secured to the lower end of said inner plunger member, cam means fixed on the end of said outer plunger member, cam follower means carried by said inner plunger member so constructed and arranged that upon relative downwardly directed axial movement of said outer plunger member with respect to said body the cam means will act on said follower means to impart a limited rotational movement to said inner plunger member, means preventing rotational movement of the outer plunger member with respect to said body, a resilient means operative between said firing pin and said inner plunger member, said resilient means arranged to oppose relative downwardly directed axial movement of said inner plunger member with respect to said body, tab means radially fixed on said firing pin and so arranged and constructed as to align with said groove means when said inner plunger member is rotationally advanced with respect to said outer plunger member by a predetermined number of axial reciprocations of said outer plunger member whereby said firing pin is freed to move downwardly under the force of said resilient means.

L25 l0 l3 2 l? m 26 I4 35 ll 3 34" I39 47 48 :9 $637 1 .'L

PATENTEUnm 19 Ian SHEET lUF2 INVENTORS RICHARD GJ'HRESHER JOHN P KOSAR JAMES F. ARPER ATTORNIY8:

PATENTEDUBT 19 ml 3,613,593

SHEET 2 BF 2 Fl G. 6.

7 FIG. 5.

Q F s o c e A W I g V omscnon OF ROTATION FIG. 7.

INVENTOR.

RICHARD G.THRESHER JOHN F. KOSAR JAMES E l 1 BY m ARPER Ar'ronuss:

MECHANICAL COUNTING FUZE The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to us of any royalty thereon.

This invention relates to a fuze for an explosive, and particularly to a mechanical counting fuze for use with an antitank or an antipersonnel mine whereby the mine may be activated by the first or by such subsequent contact as may be desired.

The mechanical counting fuze of this invention is commonly known in the fuze art as a skip" fuze. It may be used in combination with an antitank or an antipersonnel mine, and can be set to activate by the first or by such subsequent contact as may be desired. Mines using a skip type fuze as that of the present invention may be laid out in an infinite variety of patterns to impede, harass, or confuse the enemy in accordance with tactical requirements. A mine field could be laid out in a pattern wherein the mines would be set to be activated after different numbers of pressure pulses or contacts are applied to the fuze. The mines located at the beginning portion of the field could have their fuzes set for activation after a predetermined plurality of contacts. As the mines are positioned farther into the field the number of contacts necessary for their activation may progressively decrease. The mines at the most remote portion of the field may activate on one contact. In an enemy advance the first tanks or troops entering the field would contact the mines at the beginning portion of the field without activating them. The advance would continue into the field with subsequent contacts of mines being made without activation. Additional enemy advances would repeat contacts of the mines without their activation. However, each contact with a mine would bring it closer to activation. A condition will ultimately be reached where a certain number of enemy are on the mine field, and contact with any mine will result in its activation. The enemy will be trapped on the field since movement in any direction will cause a mine to activate.

Heretofore, the skip"-type mechanical counting mine fuzes known in the art had many inherent disadvantages limiting their application. The most serious defect was their complexity in structure'and operation. Especially complex were the structures comprising the pressure pulse or contact-counting portion of the fuze. Counting portion structures ranged from pawl and gear counters to elaborate cam and follower counters. Extensive machining with attendant high cost was required to provide the elements for the prior art counting structures.

Since the prior art mechanical counting fuzes were so complex in structure and economically impracticable for mass quantity use resort was had to electronic counting fuzes. Electronic type fuzes naturally require a power source for their operation. The necessity of a power source is attended by serious disadvantages, one of which is the inability of the electronic fuze to meet the -year shelf life required of mine fuzes. Current state-of-the-art in small power sources does not permit 20-year storage. Power source leakage resulting from insulation breakdown further renders the electronic fuze incapable of meeting a requirement of fuzes for maintaining active life after burial in the ground for one year.

Both the prior art mechanical and electronic skip"-type fuzes were further limited in their use in that no provisions were made for a simple means of setting the activation count of the fuze. The only way of setting the activation count was to disassemble the fuze and make the setting. This method was extremely time consuming. Furthermore, no way, outside of markings, existed for readily and positively ascertaining the fuze activation count setting. Therefore, when a prior art skip-type fuze was assembled to a mine it could not be determined whether the activation count of the fuze was prematurely changed, and if a change were required in the activation count the fuze would have to be disassembled from the mine and the involved procedure of resetting followed. As a result of the above disadvantages the prior art skip"-type mine fuzes were marginal in fulfilling military needs and, at best, af-

forded an undesirable expedient to the long-existing'need for an effective mechanical counting fuze.

It is, therefore, an object of the present invention to provide a mechanical counting fuze for an antitank or an antipersonnel mine which may be activated by the first or by such subsequent contact as may be desired, and which uses parts of simplified and low-cost construction.

It is a further object of this invention to provide a mechanical counting fuze for an antitank or an antipersonnel mine which may be activated by a first or by such subsequent contact as may be desired and which activation contact may be readily and easily set without disassembling the fuze.

it is also an object of this invention to provide a mechanical counting fuze for an antitank or an antipersonnel mine which may be activated by a first or by such subsequent contactas may be desired and which activation contact may be readily and easily set while the fuze is within or without the mine.

It is still another object of this invention to provide a mechanical counting fuze for an antitank or an antipersonnel mine which may be activated by a first or by such subsequent contact as may be desired and the activation contact setting of which may be positively ascertained by visual observation.

The invention will, however, be further understood and other objects and advantages thereof will become apparent from the following description, when considered in connection with the accompanying drawings, the scope of the present invention being pointed out in the appended claims.

In the drawings:

FIG. 1 is an elevation view partly in cross section of the inventive fuze;

FlG. 2 is a top view of the invention;

FIG. 3 is a sectional view of the invention through 3-3 of FIG. 1;

FIG. 4 is a view taken in the direction of the arrows on line 4-4 of FIG. 1; I

FIG. 5 is a development of an operative element of the present invention showing details of construction;

FIG. 6 is a top view ofFlG. 5:

FIG. 7 is an illustration of the interaction of operative elements of the present invention showing, in sequence, one operation.

Referring to the drawings, in which like reference characters refer to like parts throughout the various figures, l0 designates the mechanical counting fuze as a whole, having a cylindrical body 11 comprising an upper housing 12 and a lower housing 13. The lower housing 13 is adapted at its upper end to receive the lower end of the upper housing 12 in abutting relationship, a continuous main axial bore 14 being formed thereby in which is carried a plunger assembly 15.

The plunger assembly 15 comprises an outer plunger member 16 concentric with an inner plunger member 17. At a substantially central point of the upper housing 12 the main bore 14 has a shoulder 18 defining a reduced diameter portion of the main bore upward of such shoulder, which reduced diameter portion receives the central portion of the outer plunger member 16 in slidable relationship therewith. The latter extends upwardly beyond the end of upper housing 12 and terminates in an integrally connected fiangelike head 20. Surrounding the central portion 19 of the outer plunger member 16 and arranged between the lower surface of the head 20 and the upper surface of the upper housing 12 is a helical coil spring 21. The spring 21 is of sufficient strength to aid in returning the outer plunger member 16 to its upper position after a pressure pulse applied to the head 20, causing a downwardly directed depression of the plunger assembly 15, is released.

Below the shoulder 18 is disposed an enlarged chamber which is defined by a spline fitting 22 as shown in FIG. 3. The lower end portion of the outer plunger 16 defines a spline shaft 23 and is received in slidable relationship in the spline fitting 22. The function of the spline arrangement is to restrict outer plunger member 16 to vertical downward movement when a downward force is applied to head 20.

The lower ends of the teeth 24 of the spline shaft 23 are formed into V-shapes, each surface of the V having a 45 inclination angle with reference to the longitudinal axis of the fuze 10. As shown in FIG. 5 the teeth 22a of the spline fitting 22 have their lower ends formed into a wedgelike surface having a 45 inclination angle with reference to the longitudinal axis of the fuze 10. The function of the lower end shapes of the teeth 22a and 24 will be shown further on in the course of this description.

The lower end of the central portion 19 of the outer plunger member 16 extends into the spline shaft 23 to a point substantially at the top ofthe V of the teeth 24.

The inner plunger member 17 is concentrically disposed in rotatable and slidable relationship with the outer plunger member 16. The upper end of the inner plunger member 17 is hollow cylinder 25 have spline fitting at its inside bottom. A shaft 26 having a splined lower end oflarger diameter than its main body portion is force mated with the spline fitting of the cylinder. The upper end of the shaft 26 extends above the cylinder 25 and into the head 20 of the outer plunger member 16. A helical coil spring 27 in compression is placed around the shaft 26 with its lower end in abutment with the spline portion of the shaft 26. A retaining collar 28 having an axial opening is force fitted to the shaft 26 and is placed in abutment with the cylinder 25 and the upper end of the spring 27. The retaining collar 28 fits into an axial opening in the lower end portion of the head 20 of the outer plunger member 16. The shaft 26 adapted at its upper end to receive in fixed relationship therewith an indexing plate 29 which fits into an axial counterbore in the upper portion of the head 20. The urging of the compression spring 27 against the lower surface of the retaining collar 28 assists in holding the indexing plate 29, shaft 26, and cylinder 25 in fixed relationship with each other.

A clearance between the outer lower surface of the indexing plate 29 and the counterbore of the head 20 allows a downward displacement of the inner plunger member 17 with relation to the other plunger member 16.

The indexing plate 29 is formed with an upwardly extending flange 30. An indicator 31 passes diametrically across the surface of the indexing plate 29 and is fixed thereto. The indicator 31 is raised a sufficient amount above the surface of the indexing plate 29 so that it can be firmly gripped by an operator to enable him to rotate the inner plunger member 17 when setting the activation count of the fuze 10. When an activation count is set, the indicator 31 will align with one of the reference marks scribed on the upper surface of the head 20 of the outer plunger member 16 as shown in FIG. 2. The operation of setting the activation count will be further detailed later on in the description.

The outer periphery of the flange 30 of the indexing plate 29 is adapted to receive an O-ring seal 33 which engages the wall of the counterbore of the upper portion of the head 20. This seal functions to prevent entrance of any foreign matter into the space between the outer plunger member 16 and inner plunger member 17.

The cylinder 25 extends to a point substantially at the lower end of the spline shaft 23 of the outer plunger member 16. Disposed below the cylinder 25 and integrally a part thereof is a hub 34 having an outside diameter substantially the same as that of the central portion 19 of the outer plunger member 16. The hub defines a spline shaft having three splines 35 spaced l20 apart. The splines 35 extend radially outwardly from the hub 34 to a diameter substantially equal to that of the teeth 24 of the spline shaft 23. The circumferential width of the splines 35 is substantially the same as that of the teeth 24 of the shaft 23 and the spaces or grooves therebetween. The upper end portions of the splines 35 are formed into inclined surfaces having an angle of 45 with reference to the longitudinal axis of the fuze and equal to the angle of inclination of either side of the V portion of the teeth 24 of shaft 23. The inclined surfaces of the teeth 22a of the spline fitting 22.

The splines 35 engage three teeth 24 of the spline shaft 23, each spline 35 engaging a corresponding tooth 24 as shown in FIG. 1. When the fuze 10 is in the inactive condition as illustrated in FIG. 1 an upper portion of each of the splines 35 fits into a portion of the same spline fitting 23 groove into which its corresponding tooth 24 fits. When a pressure pulse or contact is applied to the plunger assembly 15, both the outer plunger member 16 and inner plunger member 17 will move longitudinally downwards, the teeth 24 and splines 35 sliding along their respective grooves in the spline fitting 23. When the uppermost portion of the splines 35 is moved downwardly just beyond the lowermost portion of the spline fitting 23 the teeth 24 will act on the splines 35 to rotate the inner plunger member 17. This operation will be shown in more detail further on in the description.

Axially disposed below the hub 34 and integrally connected therewith is a key shaft 36 having a square cross section. The key shaft 36 is slidably fitted into the bore 37 of a firing pin assembly 38. There is sufficient clearance between the lower end of the key shaft 36 and the inside bottom of the bore 37 to allow longitudinal movement of the key shaft 36 in the bore 37 when a pressure pulse is applied to the plunger assembly 15. The firing pin assembly 38 will not move longitudinally but will rotate about the fuze l0 axis when the plunger assembly 15 is actuated by a pressure pulse.

The firing pin assembly 38 is generally cylindrical in shape having an upper cylindrical portion 39 and an integrally connected enlarged lower portion 40 having an impinging or firing pin 41 arranged on the lower end thereof adapted to strike a primer as the firing pin assembly 38 is released. The lower portion 40 of the firing pin assembly 38 extends through the lower end of the lower housing 13. A reduced diameter opening 42 at the lower end of the main bore 14 permits the lower end portion 40 to extend through the lower end of the lower housing 13. The diameter of the opening 42 is slightly larger than the outside diameter of the lower portion 40 of the firing pin assembly 38, allowing sufficient clearance for rotation of the firing pin assembly 38 therein. As shown in FIG. 4 the opening 42 is provided with two diametrically opposite slots 43 and 44 of unequal shape.

The lower portion 40 of the firing pin assembly 38 defines a shoulder 43 on its upper end having diametrically opposite tabs 46 and 47 thereon of unequal shapes corresponding to the shapes of the slots 43 and 44 respectively. The tabs 46 and 47 extend beyond the opening 42 impeding the downward movement of the firing pin assembly 38 until such time when the tabs 46 and 47 are vertically aligned with the slots 43 and 44 respectively.

Surrounding the key shaft 36 and upper portion 29 of the firing pin assembly 38 is a helical coil spring 48 in compression. The upper end of the spring 48 is adapted to contact a lower end portion of the hub 34 while the lower end of the spring 48 is adapted to seat upon the shoulder 45 of the firing pin assembly 36. The spring 48 is of sufficient strength to cause the plunger assembly 15 to move longitudinally upwards when a pressure pulse thereon is released, and to cause the downward movement of the firing pin assembly 38 when the tabs 46 and 47 and the slots 43 and 44 are respectively vertically aligned.

An upwardly extending stop 49 is provided on the inside surface of the lower end of the lower housing 13. The stop 49 is positioned so that the tab 46 will strike it when the activation count is set at the maximum number of counts permissible. The stop 49 precludes vertical alignment of the tabs 46 and 47 and slots 43 and 44 when setting the activation count. The stop 49 is situated in a position whereby it will not interfere with the tab 47 when the firing pin assembly 38 is being rotated during operation of the fuze 10.

In operation of the fuze 10 with an antitank or antipersonnel mine the first function is to set number of activation counts desired in accordance with a tactical mission. To set the activation count the plunger assembly 15 is depressed by hand to its lowermost position and held there. The plunger assembly 15 is held depressed by applying the hand pressure to the indexing plate 29 of the inner plunger member 17 to insure that both inner and outer plunger members are in their lowermost depressed position. At the lowermost position the splines 35 are no longer within'the grooves of the splined fitting 22. The inner plunger member 17 will be free to rotate. By grasping the indicator 31 of the inner plunger member 17, while maintaining sufficient pressure to hold the plunger assembly 15 in a lowermost position, the inner plunger member 17 may be rotated in a counterclockwise direction, as viewed from the top, to the number of counts desired before activation of the fuze. The count number desired is established when the inner plunger member 17 is rotated until the arrowhead of the indicator 31 aligns with the reference mark on the upper surface of the head 29 corresponding to the desired count number.

As shown in FIG. 1 the relationship of the teeth 24 of the spline shaft 23 to the splines 35, particularly their coacting inclined surfaces, provide a unidirectional ratchet-type rotational movement between inner plunger member 17 and the stationary outer plunger member 16. In this embodiment of the invention the rotation of the inner plunger member 17 with respect to the outer plunger member 16 when setting the activation count is in a counterclockwise direction as viewed from the top and as shown in FIG. 2.

The firing pin assembly 38 will rotate with the inner plunger member 17. The tabs 46 and 47, being diametrically opposite to each other, also have their radial axis (that is, with reference to the longitudinal axis of the fuze in a coplanar parallel relationship with the radial axis (same reference) of the indicator 3]. Therefore, the orientation of the indicator 31 with reference to the slots 43 and 44 of the opening 42 in the lower end of the lower housing 13 determines the orientation of the tabs 46 and 47 with respect to the same slots 43 and 44.

After the desired count number is set the plunger assembly 15 can be returned to its upper position by slowly releasing the pressure on the inner plunger member 17 while holding the indicator 31 with sufficient force to prevent the inner plunger member 17 from rotating clockwise. The interaction of the elements of the plunger assembly 15 will cause the clockwise rotation of the inner plunger member 17 as will be shown in the description which follows of the count operation of the fuze. The activation count setting may be made before or after the fuze is assembled to a mine.

The count operation results in a prescribed incremental rotational movement of the inner plunger member 17 and the firing pin assembly 38. This incremental movement is caused by the application and release of a pressure pulse or contact on the plunger assembly 15. The operation following can be best understood by reference to F IG. 7.

When contact is made by a vehicle or foot soldier, the weight on the top of the mine depresses the plunger assembly 15. The movement of the inner plunger assembly 16, and outer plunger assembly 17 at this point is longitudinally downward. The firing pin assembly 38 remains fixed while the key shaft 36 moves longitudinally within the bore 36. The outer plunger member 16 is limited to longitudinal movements by the coaction of the spline shaft 23 and the spline fitting 22 of the upper housing 12. The inner plunger member 16 is limited to longitudinal movement until the uppermost points of the splines 35 reach the lowermost point of the spline fitting 21 (FIG. 7c). Until this position is reached the splines 35 ride in the groove portions of the spline fitting 22 along with their corresponding teeth 24 of the spline shaft 23, and rotational movement is thereby precluded. The continued depression of the plunger assembly 15 by the external contact pressure will maintain the initial orientation of the inner plunger member 17 with regard to the outer plunger member 16. When the pressure contact is removed from the plunger assembly 15 the compressive force of the spring 48 acting on the inclined surfaces of the splines 35 and the teeth 24 they are in contacting relationship which causes the splines 35 to slide over the surfaces of the teeth 24 into the next spaces between the teeth 24 (FIG. 7d). The result of this relative movement between the splines 35 and teeth 24 is a clockwise rotation of the inner plunger member 17 whileit and the outer plunger member 16 are both moving longitudinally upwards.Further rotational movement of the inner plunger member 17' will be restrained by the action on the longitudinal surface of the splines 35 of the next clockwise-oriented teeth 24 of the spline shaft 23. At this point the inner plunger member 17 is restrained-from further upward movement by the teeth" 22a actingon the splines 35. The spring 21 now acts to urge the outer plunger member 16 upwardly. When the upper-points on the V ofthe teeth 24 reach the uppermost points of the splines 35 the com pressive force of the spring 48 will cause the splines 35 to slide along the teeth 22a of the spline fitting 22 (FIG. 7e), resulting in another incremental rotation of the inner plunger member 17. As shown in FIG. 7f the sliding of the spline 35' along the teeth 22a continues until the inclined surfaces of the splines 35 contact the complementary inclined surfaces on the V of the teeth 24. At this point the plunger assembly 15 is in its upper position ready for the next count. I V

The magnitude of the rotationalincrements are determined by the number of teeth in the spline shaft 23 and spline fitting 22. In this embodiment there are 12 .teeth on each The total incremental movement, therefore, will be 30, each increment of rotation being 15.

The count operation described above is repeated each time a pressure pulse is applied to and released from the plung'erassembly 15. The firing pin assembly 38 rotates on each count until the tabs 46 and 47 are respectively vertically aligned'w'ith the slots 43 and '44 at which timethe compressive-force of the spring 48 will act on the firing pin assembly 38 to drive it downwardly to impinge against a primer resulting in detonation.

We claim: 1. A fuze comprising a body with an upper and a lower end having a main axial bore therethrough, p said body lower end having an axial bore smaller thansaid main bore and having radial .groove'means in the wall defining said smaller bore, a hollow outer plunger member slidably mounted in said main bore, an inner plunger member movably mounted plunger member and coaxial therethrough, a firing pin releasably secured to the lower end of said inner plunger member, cam means fixed on the end of said outer plunger member, cam follower means carried by saidinner plunger member so constructed and arranged that upon relative downwardly directed axial movement of said ,outer plunger member with respect to said body the cam means will act on said follower means to impart a limited rotational movement to said inner plunger member, means preventing rotational movement of the outer plunger member with respect to said body, a resilient means operative between said firing pin and said inner plunger member, said resilient means arranged to oppose relative downwardly directed axial movement of said inner plunger member with respect to said body, tab means radially fixed on said firing pin and so arranged and constructed as to align with said groove means when said inner plunger member is rotationally advanced with respect to said outer plunger member by predetermined number of axial reciprocations of said outer plunger member whereby said firing pin is freed to move downwardly under the force of said resilient means. 2. A fuze comprising g a body with an upper and a lower end having a main axial bore therethrough, said body lower end having an axial bore smaller than said main bore and having radial groove means in the wall defining said smaller bore, a hollow outer plunger member slidably mounted in said main bore, an inner plunger member movably mounted in said outer plunger member and coaxial therewith,

in said outer a firing pin releasably secured to the lower end of said inner plunger member,

cam means fixed on the end of said outer plunger member,

cam follower means carried by said inner plunger member so constructed and arranged that upon relative downwardly directed axial movement of said outer plunger member with respect to said body the cam means will act on said follower means to impart a limited rotational movement to said inner plunger member,

means preventing rotational movement of the outer plunger member with respect to said body,

a resilient means operative between said firing pin and said inner plunger member, said resilient means arranged to oppose relative downwardly directed axial movement of said inner plunger member with respect to said body,

tab means radially fixed on said firing pin and so arranged and constructed as to align with said groove means when said inner plunger member is rotationally advanced with respect to said outer plunger member whereby said firing pin is freed to move downwardly under the force of said resilient means,

means on said inner plunger member for adjusting the rotational relationship between said cam means and said cam follower means whereby the number of reciprocations of said outer plunger member necessary to align said tab means with said groove means may be varied.

3. A fuze as defined in claim 2 provided with means for indicating the setting of said number of reciproeations.

4. A fuze comprising a cylindrical body with an upper and a lower end having a main axial bore therethrough, said body defining an intermediate spline fitting having a plurality of equally spaced splines with inclined lower ends, said body lower end having an axial bore smaller than said main bore having radial groove means in the wall defining said smaller bore,

a hollow outer plunger member slidably mounted in said main bore,

a flange member coaxially fixed with said outer plunger member above the upper end of said body and in spaced relationship therewith, said flange member being provided with an axial bore,

a first helical coil spring surrounding a portion of said outer plunger member arranged between the lower surface of said flange member and the surface of said body upper end,

an inner plunger member slidably and rotatably mounted in said outer plunger member and coaxial therewith,

a shaft having rectangular cross section coaxially fixed to the lower end of said inner plunger member,

a firing pin slidably mounted to the lower end of said shaft,

a spline shaft coaxially fixed to the lower end of said outer plunger member defining a plurality of equally spaced splines having V-shaped lower ends, said spline shaft mating in slidable relationship with said spline fitting whereby only axial movement of said outer plunger with respect to said body is permitted,

a plurality of teeth having inclined upper ends longitudinally fixed to the periphery of the lower end portion of said inner plunger member and equally spaced with respect to each other, said teeth inclined upper ends contacting one side of the lower end V-shaped portions of said spline shaft splines whereby upon relative downwardly directed axial movement of said outer plunger member with respect to said body said spline shaft will coact with said teeth to impart a downwardly directed axial movement and a limited rotational movement to said inner plunger member,

a second helical coil spring surrounding said rectangular shaft operative between said firing pin and said inner plunger member,

part a force to said teeth which will coact with said spline-fitting splines to advance said inner plunger member another limited rotation increment,

a tab radially fixed on said firing pin so arranged and constructed as to align with said groove means when said inner plunger member is rotationally advanced with respect to said outer plunger member by a predetermined number of axial reciprocations of said outer plunger member whereby said firing pin is freed to move downwardly under the force of said second helical coil spring.

5. A fuze comprising a cylindrical body with an upper and a lower end having a main axial bore therethrough, said body defining an intermediate spline fitting having a plurality of equally spaced splines with inclined lower ends, said body lower end having an axial bore smaller than said main bore and having radial groove means in the wall defining said smaller bore,

a hollow outer plunger member slidably mounted in said main bore,

a flange member coaxially fixed with said outer plunger member above the upper end of said body and in spaced relationship therewith, said flange member being provided with an axial bore, said flange member having number characters scribed on the upper surface thereof spaced equally in relationship to and increasing in order in correspondence with the number of said spline-fitting splines,

a first helical coil spring surrounding a portion of said outer plunger member arranged between the lower surface of said flange member and the surface of said body upper end,

an inner plunger member slidably and rotatably mounted in said outer plunger member and coaxial therewith,

a plate member coaxially fixed to the upper end of said inner plunger member and fitted into said flange member axial bore,

a rod member having a pointer fixed on one end thereof diametrically fixed to the upper surface of said plate member,

a shaft having a rectangular cross section coaxially fixed to the lower end of said inner plunger member,

a firing pin slidably mounted to the lower end of said shaft,

a spline shaft coaxially fixed to the lower end of said outer plunger member defining a plurality of equally spaced splines having V-shaped lower ends and corresponding in number to said spline-fitting splines,

said spline shaft mating in slidable relationship with said spline fitting whereby only axial movement of said outer plunger with respect to said body is permitted,

a plurality of teeth having inclined upper ends longitudinally fixed to the periphery of the lower end portion of said inner plunger member and equally spaced with respect to each other, said teeth inclined upper ends contacting one side of the lower end V-shaped portions of said spline shaft splines whereby upon relative downwardly directed axial movement of said outer plunger member with respect to said body said spline shaft will coact with said teeth to impart a downwardly directed axial movement and a limited rotational movement to said inner plunger member,

a second helical coil spring surrounding said rectangular shaft operative between said firing pin and said inner plunger member, said second helical coil spring arranged to oppose relative downwardly directed axial movement of said inner plunger member with respect to said body whereby upon upwardly directed axial movement of said inner plunger member said second helical coil spring will impart a force to said teeth which will coact with said spline-fitting splines to advance said inner plunger member another limited rotational increment,

a tab radially fixed on said firing pin and in coplanar parallel relationship with said rod member so arranged and constructed as to align with said groove means when said inner plunger member is rotationally advanced with respect to said outer plunger member by a predetermined number of axial reciprocations of said outer plunger member, the number of predetermined reciprocations identifiable by the numeral character on the surface of said flange member aligned with said rod member pointer, whereby said firing pin is freed to move downwardly under the force of said second helical coil spring.

6. A fuze as defined in claim 5 further characterized by a longitudinally extending stop member fixed to the inside surface of said body lower end and positioned with respect to said groove means whereby said tab will strike said stop member when said inner plunger member is rotated in a direction to set the number of axial reciprocations of the outer plunger member necessary to align said tab with said groove means. 

1. A fuze comprising a body with an upper and a lower end having a main axial bore therethrough, said body lower end having an axial bore smaller than said main bore and having radial groove means in the wall defining said smaller bore, a hollow outer plunger member slidably mounted in said main bore, an inner plunger member movably mounted in said outer plunger member and coaxial therethrough, a firing pin releasably secured to the lower end of said inner plunger member, cam means fixed on the end of said outer plunger member, cam follower means carried by said inner plunger member so constructed and arranged that upon relative downwardly directed axial movement of said outer plunger member with respect to said body the cam means will act on said follower means to impart a limited rotational movement to said inner plunger member, means preventing rotational movement of the outer plunger member with respect to said body, a resilient means operative between said firing pin and said inner plunger member, said resilient means arranged to oppose relative downwardly directed axial movement of said inner plunger member with respect to said body, tab means radially fixed on said firing pin and so arranged and constructed as to align with said groove means when said inner plunger member is rotationally advanced with respect to said outer plunger member by predetermined number of axial reciprocations of said outer plunger member whereby said firing pin is freed to move downwardly under the force of said resilient means.
 2. A fuze comprising a body with an upper and a lower end having a main axial bore therethrough, said body lower end having an axial bore smaller than said main bore and having radial groove means in the wall defining said smaller bore, a hollow outer plunger member slidably mounted in said main bore, an inner plunger member movably mounted in said outer plunger member and coaxial therewith, a firing pin releasably secured to the lower end of said inner plunger member, cam means fixed on the end of said outer plunger member, cam follower means carried by said inner plunger member so constructed and arranged that upon relative downwardly directed axial movement of said outer plunger member with respect to said body the cam means will act on said follower means to impart a limited rotational movement to said inner plunger member, means preventing rotational movement of the outer plunger member with respect to said body, a resilient means operative between said firing pin and said inner plunger member, said resilient means arranged to oppose relative downwardly directed axial movement of said inner plunger member with respect to said body, tab means radially fixed on said firing pin and so arranged and constructed as to align with said groove means when said inner plunger member is rotationally advanced with respect to said outer plunger member whereby said firing pin is freed to move downwardly under the force of said resilient means, means on said inner plunger member for adjusting the rotational relationship between said cam means and said cam follower means whereby the number of reciprocations of said outer plunger member necessary to align said tab means with said groove means may be varied.
 3. A fuze as defined in claim 2 provided with means for indicating the setting of said number of reciprocations.
 4. A fuze comprising a cylindrical body with an upper and a lower end having a main axial bore therethrough, said body defining an intermediate spline fitting having a plurality of equally spaced splines with inclined lower ends, said body lower end having an axial bore smaller than said main bore having radial groove means in the wall defining said smaller bore, a hollow outer plunger member slidably mounted in said main bore, a flange member coaxially fixed with said outer plunger member above the upper end of said body and in spaced relationship therewith, said flange member being provided with an axial bore, a first helical coil spring surrounding a portion of said outer plunger member arranged between the lower surface of said flange member and the surface of said body upper end, an inner plunger member slidably and rotatably mounted in said outer plunger member and coaxial therewith, a shaft having rectangular cross section coaxially fixed to the lower end of said inner plunger member, a firing pin slidably mounted to the lower end of said shaft, a spline shaft coaxially fixed to the lower end of said outer plunger member defining a plurality of equally spaced splines having V-shaped lower ends, said spline shaft mating in slidable relationship with said spline fitting whereby only axial movement of said outer plunger with respect to said body is permitted, a plurality of teeth having inclined upper ends longitudinally fixed to the periphery of the lower end portion of said inner plunger member and equally spaced with respect to each other, said teeth inclined upper ends contacting one side of the lower end V-shaped portions of said spline shaft splines whereby upon relative downwardly directed axial movement of said outer plunger member with respect to said body said spline shaft will coact with said teeth to impart a downwardly directed axial movement and a limited rotational movement to said inner plunger member, a second helical coil spring surrounding said rectangular shaft operative between said firing pin and said inner plunger member, said second helical coil spring arranged to oppose relative downwardly directed axial movement of said inner plunger member with respect to said body whereby upon upwardly directed axial movement of said inner plunger member said second helical coil spring will impart a force to said teeth which will coact with said spline-fitting splines to advance said inner plunger member another limited rotation increment, a tab radially fixed on said firing pin so arranged and constructed as to align with said groove means when said inner plunger member is rotationally advanced with respect to said outer plunger member by a predetermined number of axial reciprocations of said outer plunger member whereby said firing pin is freed to move downwardly under the force of said second helical coil spring.
 5. A fuze comprising a cylindrical body with an upper and a lower end having a main axial bore therethrough, said body defining an intermediate spline fitting having a plurality of equally spaced splines with inclined lower ends, said bOdy lower end having an axial bore smaller than said main bore and having radial groove means in the wall defining said smaller bore, a hollow outer plunger member slidably mounted in said main bore, a flange member coaxially fixed with said outer plunger member above the upper end of said body and in spaced relationship therewith, said flange member being provided with an axial bore, said flange member having number characters scribed on the upper surface thereof spaced equally in relationship to and increasing in order in correspondence with the number of said spline-fitting splines, a first helical coil spring surrounding a portion of said outer plunger member arranged between the lower surface of said flange member and the surface of said body upper end, an inner plunger member slidably and rotatably mounted in said outer plunger member and coaxial therewith, a plate member coaxially fixed to the upper end of said inner plunger member and fitted into said flange member axial bore, a rod member having a pointer fixed on one end thereof diametrically fixed to the upper surface of said plate member, a shaft having a rectangular cross section coaxially fixed to the lower end of said inner plunger member, a firing pin slidably mounted to the lower end of said shaft, a spline shaft coaxially fixed to the lower end of said outer plunger member defining a plurality of equally spaced splines having V-shaped lower ends and corresponding in number to said spline-fitting splines, said spline shaft mating in slidable relationship with said spline fitting whereby only axial movement of said outer plunger with respect to said body is permitted, a plurality of teeth having inclined upper ends longitudinally fixed to the periphery of the lower end portion of said inner plunger member and equally spaced with respect to each other, said teeth inclined upper ends contacting one side of the lower end V-shaped portions of said spline shaft splines whereby upon relative downwardly directed axial movement of said outer plunger member with respect to said body said spline shaft will coact with said teeth to impart a downwardly directed axial movement and a limited rotational movement to said inner plunger member, a second helical coil spring surrounding said rectangular shaft operative between said firing pin and said inner plunger member, said second helical coil spring arranged to oppose relative downwardly directed axial movement of said inner plunger member with respect to said body whereby upon upwardly directed axial movement of said inner plunger member said second helical coil spring will impart a force to said teeth which will coact with said spline-fitting splines to advance said inner plunger member another limited rotational increment, a tab radially fixed on said firing pin and in coplanar parallel relationship with said rod member so arranged and constructed as to align with said groove means when said inner plunger member is rotationally advanced with respect to said outer plunger member by a predetermined number of axial reciprocations of said outer plunger member, the number of predetermined reciprocations identifiable by the numeral character on the surface of said flange member aligned with said rod member pointer, whereby said firing pin is freed to move downwardly under the force of said second helical coil spring.
 6. A fuze as defined in claim 5 further characterized by a longitudinally extending stop member fixed to the inside surface of said body lower end and positioned with respect to said groove means whereby said tab will strike said stop member when said inner plunger member is rotated in a direction to set the number of axial reciprocations of the outer plunger member necessary to align said tab with said groove means. 